Collection of Data: Sources, Methods, Sampling and Questionnaire Basics Questions

Question 1

Define primary data.

Accepted Answer

Primary data are data collected first-hand by the investigator for the specific study.

Question 2

Define secondary data.

Accepted Answer

Secondary data are data already collected by others and used for the current study.

Question 3

What is a census method?

Accepted Answer

Census method means collecting data from every unit of the population.

Question 4

Define sampling.

Accepted Answer

Sampling is selecting a representative subset of the population to study and draw conclusions about the population.

Question 5

What is a questionnaire?

Accepted Answer

A questionnaire is a set of written questions used to collect information from respondents.

Question 6

What is sampling error?

Accepted Answer

Sampling error is the difference between a sample result and the true population value due to studying only a sample.

Question 7

Differentiate between primary data and secondary data (any three points).

Accepted Answer

Primary and secondary data differ as follows:

| Point | Primary data | Secondary data |
|---|---|---|
| Source | collected first-hand | collected earlier by others |
| Cost/time | higher | lower |
| Suitability | specific to objective | may not fit perfectly |

(Any three points can be written.)

Question 8

Write any three methods of collecting primary data.

Accepted Answer

Methods of collecting primary data include:

1) Direct personal investigation/interview.
2) Observation method.
3) Questionnaire or schedules through enumerators.

(Any three methods can be written.)

Question 9

Write any three sources of secondary data.

Accepted Answer

Sources of secondary data include:

1) Government publications (census, reports).
2) Company records (sales, accounts).
3) Journals, research reports and websites/databases.

(Any three sources can be written.)

Question 10

Differentiate between census and sample survey (any three points).

Accepted Answer

Difference:

| Point | Census | Sample survey |
|---|---|---|
| Coverage | all units | subset |
| Cost/time | high | lower |
| Suitability | small population | large population |

(Any three points can be written.)

Question 11

Explain probability and non-probability sampling (any three points).

Accepted Answer

Difference:

1) Probability sampling: each unit has a known chance of selection (random).
2) Non-probability sampling: selection is based on convenience/judgment, chance not known.
3) Probability sampling is generally more representative and supports valid inference than non-probability sampling.

(Any three points can be written.)

Question 12

Write any three features of a good questionnaire.

Accepted Answer

Features of a good questionnaire include:

1) Simple, clear and unambiguous questions.
2) Logical order and appropriate length.
3) Avoids leading questions; pilot tested before final use.

(Any three features can be written.)

Question 13

Explain primary and secondary data, with advantages and limitations of each.

Accepted Answer

Data can be collected from two main sources: primary and secondary.

**Primary data** are collected first-hand by the investigator for the specific purpose of the study (through survey, interview, observation, questionnaire, etc.). **Secondary data** are already collected by someone else and are available in published or unpublished form (government reports, company records, journals, websites).

| Point | Primary data | Secondary data |
|---|---|---|
| Advantage | specific to objective; more control | cheaper; quick availability |
| Limitation | costly and time-consuming | may be outdated or not suitable |

Primary data is more suitable when accurate and specific information is required. Secondary data is useful for background study, trend analysis and preliminary research.

Thus, the choice depends on time, cost, purpose and availability of reliable data.

Question 14

Explain sampling and compare probability and non-probability sampling with a table.

Accepted Answer

Sampling is the process of selecting a representative subset from a population to study, so that conclusions about the population can be made with less cost and time than a census.

Sampling methods are broadly classified into probability and non-probability sampling.

| Category | Main idea | Examples | Suitability |
|---|---|---|---|
| Probability sampling | known chance of selection for each unit | simple random, stratified, systematic, cluster | better representativeness and inference |
| Non-probability sampling | selection based on ease/judgment; chance unknown | convenience, quota, judgment, snowball | exploratory studies, limited time |

Probability sampling reduces selection bias and provides more reliable results, but it may require a sampling frame and more planning. Non-probability sampling is easier but may be biased.

Therefore, for scientific and generalizable results, probability sampling is preferred whenever possible.

Question 15

Explain questionnaire design steps with a flowchart and write precautions in data collection.

Accepted Answer

A questionnaire is a set of written questions used to collect information from respondents. A well-designed questionnaire is essential for valid and reliable data.

Steps in questionnaire design:

```mermaid
flowchart LR
  A[Define objectives] --> B[Decide information needed]
  B --> C[Draft clear, unbiased questions]
  C --> D[Choose response format]
  D --> E[Arrange order & layout]
  E --> F[Pilot test]
  F --> G[Revise and finalize]
```

Precautions in data collection:

1) Clearly define study objectives and target respondents.
2) Use a proper sampling frame and suitable sampling method.
3) Avoid leading questions; ensure confidentiality to reduce response bias.
4) Train enumerators/interviewers and verify data through editing and checking.

Thus, good questionnaire design and careful data collection practices ensure accurate and meaningful statistical results.

Point	Primary data	Secondary data
Source	collected first-hand	collected earlier by others
Cost/time	higher	lower
Suitability	specific to objective	may not fit perfectly

Collection of Data: Sources, Methods, Sampling and Questionnaire Basics

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